According to Wikipedia: A diamanté (also spelled diamante) is a glittering ornament, such as an artificial jewel, rhinestone (named from the river Rhine where rock crystals were gathered), paste or sequin; a diamond simulant originally made from rock crystal but since the 19th century from crystal glass (i.e. lead glass) or polymers such as acrylic. The term ‘crystal’ tends to be reserved for high quality glass stones made by Czech manufacturers such as Swarovski.
According to one online store, the use of decorative rhinestone buttons dates back to the early 14th century. In more recent times, they have often been used for bridal wear and evening gowns. On dresses, blouses and accessories, diamentes seem to have been fashionable from the 1930s to the 1950s.
General Plastics/Beauclaire brand, c.1953
G. Herring/Beutron brand